What Is The Best Synthetic Underlayment?


If you are considering a new roof or re-roofing project, you probably are principally concerned about the type of tile or shingle to use. Given the roof will be around for 20 to 40 years, you want something you can live with. But if you want that roofing material to do its job effectively, there is another element that deserves your consideration — underlayment. Tar paper is the traditional underlayment, but newer, more substantial, more water-resistant materials are available and recommended by roofers. So the question becomes what the best synthetic underlayment is?

Underlayment is your roof’s first line of defense against rain, snow, cold, and, most importantly in Arizona, heat. It is placed directly on the roof deck and protects it should a tile or shingle blow off or otherwise fail. Tar paper, also known as asphalt-saturated felt, was the underlayment of choice until the advent of synthetic underlayments. Unfortunately, felt has a nasty habit of wrinkling and tearing during installation requiring time-consuming rework to repair. It provides some protection from moisture but can break down in extreme heat. Something better was needed and that’s why synthetics began appearing on the scene.

What to Look For in a Synthetic Underlayment

Generally speaking, synthetic underlayment is more expensive than tar paper, but when considered a percentage of your total roofing cost, the difference is negligible compared to the benefits. There are many synthetic brands, but typically they are made of polypropylene or polyethylene, with an asphalt-saturated basemat. Synthetic underlayment is fungus-resistant, wrinkle-free, lightweight, and stands up to UV radiation very well.

It is lighter than tar paper, is far more water-resistant, holds a roofing nail better, and doesn’t wrinkle.

There are, however, some considerations when choosing a synthetic underlayment.

  • Be sure that the underlayment is appropriate for the roofing material (tile, shingle, or metal) you are installing. There is no “one type works with everything” underlayment.
  • Pay attention to the fire rating. Underlayment is rated A, B, C, or D in flame resistance, with A being best and D being worst.
  • If you have a steep roof or many valleys, you will want an underlayment with a self-adhesive feature to ensure no slippage of coverage.
  • In Arizona, the color of the underlayment makes a difference. A light gray material can reduce the temperature of the roof deck by as much as 30 degrees compared to a black-colored underlayment. A hot roof deck translates to a higher ambient temperature in the attic, where AC air handling has to work harder to keep the air cool.

Cost is always a consideration. Synthetic underlayment is more expensive than tar paper. As a Mesa area homeowner, you might be wondering if you really need the extra moisture protection provided by synthetic given rain is an infrequent event. At ROOFSTAR Arizona, we typically recommend synthetic underlayment, given the total benefits over tar paper. The price difference will be small, and when you consider the significantly higher cost of the total project, it makes sense to protect it with the best material you can afford.

At Roofstar Arizona, we will tell you the truth about your roof. Our inspections, not the competition, drive our quotes. We will tell you what we recommend to provide you with a strong, durable roof and its cost. We don’t oversell or take shortcuts to lower prices. If you want a roofer with a history of integrity and excellent customer service, call us at (480) 426-1915 and schedule a roof inspection. Give us a call now!

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